One aspect of current semiconductor wafer processing generally involves forming dielectric layers alternating between metal layers on a semiconductor wafer. The formation of each layer, either dielectric or metal, often results in a conformal layer which corresponds to underlying surface topography. Planarization of the surface of these layers is frequently required. The art provides various methods for planarizing the wafer surface. One such method employs abrasive polishing to remove protrusions along the surface of the top layer on the semiconductor wafer. In this method, the semiconductor wafer is placed faced down on a table covered with a polishing pad which has been coated with a slurry or abrasive material. Both the wafer and the table are then rotated relative to each other to remove the protrusions on the surface of the wafer. This process of planarizing the wafer surface is generally referred to as chemical mechanical polishing (CMP).
An important part of the CMP process is the rinsing of the wafer and polishing pad. Presently, a tube is attached to the CMP equipment to dispense liquids onto the polishing pad at the center of the pad. The liquid being used for the rinsing step is water, although the tube is also equipped to dispense the slurry materials used in the polishing step. The tube extends toward the center of polishing pad and merely dispenses the water through an open hole at the end of the tube. This method relies on the centrifugal force generated by the rotation of the polishing pad to distribute the water over the entire surface of the polishing pad.
However, the prior art method has several disadvantages. One such disadvantage is that the water tends to travel radially outward from the center of the polishing pad in channels or rivulets instead of being evenly distributed over the entire surface area of the polishing pad as desired. The surface area between the water channels can remain dry. Consequently, uneven wetting of the polishing pad occurs, and the resulting polishing surface becomes non-uniform. This degradation in polishing pad surface results in low, unstable, and unpredictable polish rates leading to a non-uniform polished wafer surface which is undesirable. Another disadvantage is that the non-uniform polishing also shortens the useful life of the polishing pad which must then be replaced leading to longer equipment down time as well as adding to the cost of CMP.
Thus, a method for attaining a uniform wetting and rinsing of the polishing pad to maintain a saturated and stable surface for polishing to avoid an uneven polished wafer surface is desired.